Tesla recently disclosed plans for a $5 billion "Gigafactory" to make advanced batteries for cars like the Model S. But the Palo Alto, Calif.-based company also said it will use some of the batteries for "stationary storage applications," according to documents filed with the Securities and Exchange Commission.

The company said in the filing that it also plans to start selling batteries for homes, commercial sites and utilities.

CEO Elon Musk touts Tesla's lithium-ion battery pack technology, developed with help from Panasonic, as the best in the business. And some investors hope Tesla will apply that technology outside cars.

Tesla sees the Gigafactory as key to bringing down battery prices and making electric vehicles more affordable. By the time it reaches full production in 2020, the proposed plant would produce enough batteries for 500,000 cars. The factory's economies of scale could cut battery costs more than 30 percent, according to the company estimates.

Tesla said it's considering sites in Texas, Nevada, Arizona and New Mexico for the factory that would employ 6,500 workers.

On Thursday, a spokeswoman for Texas Gov. Rick Perry declined to comment on "potentially ongoing negotiations" between the state and Tesla over the battery factory. But Mario Hernandez, president of the San Antonio Economic Development Foundation, confirmed that Tesla had submitted an inquiry to the state.

Large-scale energy storage could strengthen the performance of electrical grids and prevent blackouts, experts say. The technology could also supplement the variable amounts of electricity flowing from solar plants and wind farms. A 2012 Pike Research report estimated that the market for grid-scale storage will reach $30 billion by 2022.

Earlier this week, Tesla stock soared after a Morgan Stanley analyst published a report arguing the company could seize a commanding role in the energy storage industry.

"If it can be a leader in commercializing battery packs, investors may never look at Tesla the same way again," analyst Adam Jonas wrote.

Tesla's stock closed Thursday at $252.54, up 20 percent from a week ago.

The company agreed to supply battery packs to one of Musk's other companies - SolarCity in San Mateo, Calif. - for a new energy management service offered to businesses as a way to cut their utility bills. SolarCity, where Musk serves as chairman, is developing a similar service for homes.

The goal of large-scale energy storage at an affordable price has proved elusive, bankrupting multiple startups over the years. And not all analysts are convinced storage will become a key market for Tesla.

"I would say, eventually, yes, grid-type storage will become a big deal. But we've got to see prices come way, way down between here and there. … I doubt it's going to be essential to Tesla's business plan," said Craig Irwin of Wedbush Securities.